Chris Froome's blood and urine samples from the 2015 Tour de France will be kept for 10 years in case retrospective analysis is required, cycling's world governing body has announced.

The 30-year-old Kenya-born Briton's performance in winning a second Tour title was subject to innuendo and allegation, all unsubstantiated.

The sport has a troubled history and the authorities are keen to guard against drug cheats if technology develops with the UCI, the Cycling Anti-Doping Foundation (CADF) and French Anti-Doping Agency (AFLD) announcing on Friday that samples from the top five finishers at Grand Tours will be stored for a decade.

"The UCI, the CADF and the AFLD have agreed to keep the samples for potential retrospective analyses in the future," a statement read.

"As for all Grands Tours, all the collected samples concerning the best five riders in the general classification will be kept for 10 years for potential retrospective analyses."

A total of 656 anti-doping controls - 482 were blood tests and 174 urine tests - were carried out during the race, which began in Utrecht on July 4 and finished in Paris on July 26, with Team Sky's Froome in the race winner's yellow jersey ahead of Colombian Nairo Quintana and Spain's Alejandro Valverde.

The blood tests were analysed in relation to the biological passport, which is a longitudinal way to assess for irregularities which may indicate use of performance-enhancing drugs.

Froome's critics pointed to power data as evidence of malpractice, but he was tested repeatedly while in the race leader's yellow jersey and targeted testing was in place. Froome and Team Sky have repeatedly and vehemently denied any wrongdoing.

CADF director Dr Francesca Rossi said "the targeted control strategy was discussed daily taking into account the performance of riders and other data".

Rossi added: "We strengthened our strategy of targeted controls thanks to the use of information provided by numerous sources and to the support of an intelligence coordinator."

UCI president Brian Cookson said: "We can be confident of the robustness of our programme."

Katusha's Italian rider Luca Paolini was expelled from the race after testing positive for cocaine, a recreational drug.